Exemplary embodiments of the present invention relate to a semiconductor integrated circuit, and more particularly, to an image sensor.
An image sensor refers to a device which captures an image by using semiconductor properties that respond to light. A charge coupled device (CCD) image sensor has been widely used. As the complementary-metal-oxide-semiconductor (CMOS) technology has rapidly advanced, a CMOS image sensor has been developed. As opposed to a CCD image sensor, a CMOS image sensor has an advantage in that an analog control circuit including a pixel array and a digital control circuit can be directly implemented on a single integrated circuit.
A CMOS image sensor includes a pixel array including a plurality of pixels typically configured in a matrix form. In addition, the CMOS image sensor includes a plurality of analog-to-digital conversion (ADC) units which receive analog information from each column of the pixel array and convert the received analog information into digital values. The CMOS image sensor can reproduce a realistic image when the digital values provided from the ADC units exactly correspond to analog signals provided from pixels. However, due to an offset component generated by inherent characteristics of an integrated circuit, it is difficult to reproduce an image exactly corresponding to image information inputted to the pixel arrays.